Railway control system

ABSTRACT

A railway control system is provided in which one loop of wire extends for the length of a block along each block. The length of the trackway is divided into blocks. Provision is made for exciting each wire loop with a signal current. Each train has means for detecting signal current being present in a wire loop in response to which a train car continues to run. However, there is also provided a means responsive to the presence of a train within a block to remove signal current from the wire loop in the block preceding the one in which the train is. As a result, the possibility of a rear end collision is eliminated. Also start up of all trains is made sequential. Provision is also made for sensing that all flights moving in one direction have been cleared from a single line trackway before any flights moving in the other direction are permitted to enter that trackway.

United States Patent [72] inventor Geza Horeczky Pacific Palisades, Calif. [2]] Appl. No. 751,415 [22 Filed Aug. 9, 1968 [45] Patented Jan. 5, 1971 [73] Assignee The Dashaveyor Company Venice, Calif. a corporation of California 54] RAILWAY CONTROL SYSTEM 9 Claims, 6 Drawing Figs.

[52] US. Cl .i 246/63, 246/187 [51] 1nt.Cl B61l3/18 [50] Field ofSearch 246/34, 63, 182,187B,28,63,167,187A

[56] References Cited UNITED STATES PATENTS 3,227,870 H1966 Joyce 246/34 3,234,377 2/1966 Davison et al. 246/63 Primary Examiner-Arthur L. LaPoint Assistant E.raminerGeorge H. Libman Atiorneys-Samuel Lindenberg and Arthur Frieilich ABSTRACT: A railway control system is provided in which one loop of wire extends for the length of a block along each block. The length of the trackway is divided into blocks. Provision is made for exciting each wire loop with a signal current. Each train has means for detecting signal current being present in a wire loop in response to which a train car continues to run. However, there is also provided a means responsive to the presence of a train within ablock to remove signal current from the wire loop in the block preceding the one in which the train is. As a result, the possibility ofa rear end col iision is eliminated. Also start up of all trains is made sequential. Provision is also made for sensing that all flights moving in one direction have been cleared from a single line trackway before any flights moving in the other direction are permitted to enter that trackway.

PATENTED JAN 5 I971 SHEEI 2 0F 5 Q24 N mQQSOQ zorcqjiao m i o i 2 V GB.

PATENTEU JAN 5 I97! SHEET 5 OF 5 BLOCK BLOCK 2 v/ m R m o R W o A H A Hm G B 5 m w 41 G W TUR- AN W mw mwos SOP RAILWAY CONTROL SYSTEM BACKGROUND OF TI- IE INVENTION 1. Field of the Invention This invention relates to control systems used to prevent collisions between railway trains, and more particularly to improvements therein. Y

2. Description of the Prior Art Where a railway train is driven by a human being, railway signaling indicating the presence of other trains has been carried out by colored light systems or mechanical warning systems. On occasion these have been supplemented by systems which automatically cause a train to come to a halt when it is too close to a train which is in front of it. Of course, where the railway cars are not controlled by a human being, automatic control systems are used for insuring that no collision will occur. f

The present invention is used with flights or trains of cars which are not controlled by a human being. Furthermore, by way of exempliflcation, and not by way of limitation, the present invention is used to prevent collisions on a railway system of a type which uses a single trackway with strategically placed bypass loops and end loops vin the trackway to enable the single trackway to be used for traffic in both directions. Railway systems of a type with which this invention are used are described and claimed in Pat. Application Ser. No. 69I,383, filed Dec. 18, I967 and Pat. Application Ser. No. 539,421, filed Apr. 1, 1966, and now U.S. Pat. No. 3,429,280.

OBJECTS AND SUMMARY OF THE INVENTION It is a feature of this invention that the apparatus for effectuating the kind of control briefly described above is relatively simple and inexpensive.

It is another feature of this invention that the apparatus for obtaining the operation specified above is distributed along the trackway. That is, each section of trackway has its own control apparatus and is not connected back to a central location where the control function is carried'out and commands are sent back to the location at which the control function is to be performed.

The foregoing and other features of this invention are achieved in an arrangement whereby the trackway is divided into blocks of a predetermined length. The length of a block is normally determined as the distance required for a train to come to a stop from the speed atwhich it is permitted to travel. A wire loop which may be called a control loop, is provided for each block. Provision is made so that each wire loop may be excited by a signal at a suitable frequency. Each flight has a means for picking up the signalfrequency which is radiated by the loop. Provision isalsomade to detect the presence of a flight within a block in response to which the signaling frequency in the control loops for one or more preceding blocks is removed. Where a loop for a block does not have an exciting frequency applied-thereto, a flight within such a block will automatically cut off its power and set its brakes.

The novel features of the invention are set forth with particularity in the appended claims. The invention will best be understood from the following description when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF ,THE DRAWINGS FIG. I exemplifies a track layout of atype for which this invention may be used.

FIG. 2 illustrates the track, power rail, and control loop arrangement which may be used in accordance herewith.

FIG. 3 is a perspective view, illustrating the control loop layout and associated apparatus.

FIG. 4 is a schematic illustration of the apparatus carried on a train for use with this invention, and i FIGS. 5A and 5B are a circuit diagram of the control loop arrangement in accordance with this invention.

DESCRIPTION OF THE PREFERRED-EMBODIMENTS FIG. 1 is shown by way of exemplification and is not to be construed as a limitation upon theinvention. It shows a track layout of the type with which this invention'may be employed. The track layout is designed to carry a plurality of trains, each of which has designated as a flighthereafter, and each of which consists of a plurality of cars. Either the lead car may have the necessary equipment to provide the locomotive function as well as to respond to the control function. or this may be in each one of the cars. This isdetermined by the requirements for traction. Each flight is under automatic control at all times.

Further by way of illustration and not to serve as a limitation upon the invention, a control system in accordance with this invention was developed for use with a conveyor system wherein each flight and the tracksand the associated control wiring are all enclosed within a tube. :Each car ofa flight has a door arrangement whereby it may be automatically opened, while the train is in motion, the car may be loaded, and the door may thereafter be automatically closed. Provision is also made for turning over each flight thereafter opening the doors automatically so that the flight may be unloaded.

The track layout shown in FIG. 1 has a loop 10 which may be designated as the loading loop wherein the train of cars may be loaded with cargo. At the entrance to the loop there is placed a switch 12. The switch slides a section of track, in well-known fashion whereby a flight coming from the left into the loop will be routed around the top. of the loop. The switch is'moved back to enable the flight to leave the loop and enter the main track section 14. At approximately the center of the track section 14 there is a bypass track section 16. This is provided for the purpose of enabling flights coming from one direction to be sidetracked until flights coming from the other direction pass thereby. A second track switch 18 and a third track switch 20 are placed at either end of the bypass loop to switch the track so that a flight coming from the left can enter onto the bypass section until the flight coming from the right passes it, and to enable a flight coming from the right to enter the bypass section to permit a flight. coming from the left to bypass it. 1

The loop shown on the left side of the drawing is a discharge loop section 22. It has provision for discharging the contents the block location. In the discussion that follows hereafter it v will be shown how each flight controls the number of blocks behind it to insure that, even if it comes to a stop, it will not be crashed into from the rear, despite the fact that thereis no human being at the control of the flight: It should be understood that the blocks behind the block through which a flight is moving may be referred to herein as the preceding blocks. FIG. 2 illustrates, by way of example, a track and control equipment arrangement, in accordance with this invention. Rails 30, 32 upon which a flight-34 runs, are shown as being supported in the sidewalls of a tube 36. On one side of the tube, at the upper side of the wall are three power rails respectively 37, 38 and 39. Each of these carry one phase of electrical current. On the opposite wall of the tube there is supported a signal rail 40. There is a separate signal rail for each block which is electrically isolated from every other signal rail in every other block.

Under each rail 30, 32, there is supported a first and second control wire loop respectively 42, 44. There is a first and second loop for each block. The control loops of each block are electrically isolated from the loops of every other block. A block control box 46 contains the associated equipment whereby the control for energizing and deenergizing wire loops in each block is placed. The details of this will become clearer as this discussion progresses.

Succinctly stated, in every empty block except those which immediately follow a block containing a flight, audio frequency excitation is applied to the control loops. This is detected by a small pickup coil 68 on each flight. The coil 68 extends between the wires of a loop.

The pickup coil is positioned on the left side of a flight so that when it is facing in one direction it can only detect signals in the first control loops and when facing in the opposite direction the pickup loop extends between the sides of and is responsive only to the second control loops. So long as an audio signal is present, and detected by the pickup coil power will continue to be applied to a flight. When this signal ceases, not only is power for driving the electrical motors ofthe flight turned off, but also the brakes of the flight are set to bring it to a stop as quickly as possible. If a flight is proceeding from a location at which each one of the flights will empty their loads, which may be designated as the flight empty direction, then the flight removes an audio signal from the loops in the block immediately succeeding the block in which the flight is moving. If the flight is coming from a direction in which a flight normally receives a load, then the flight removes the signal from the loops in the two blocks immediately succeeding the flight.

FIG. 3 is a perspective view showing the placement of several of the command loops, respectively 42A, 42B, 42C, and 44A, 44B, 44C. As previously'indicated, there is a loop placed underneath each of the tracks. Each loop extends for the distance of a block. Each loop, such as 44B, extends to a relay box 48. The relay box connects to a power junction box 50. The power junction box receives alternating current energy from the power rails 37 and 38 through the fuse box 50, supplies some of this to the signal rail 40 for each block through a fuse box 41, and rectifies'the remainder and supplies it to relays in the relay box 48. There is one power junction box, one relay box one fuse box 52 and one fuse box 41, for each block of track. The relay box 48 connects through wires 54 to a relay box 48A ofa preceding block and also connects through wires 56 to the relay box 488 of a succeeding block.

FIG. 4 illustrates the arrangement of the brushes which are carried in a flight for the purpose of contacting the power rail and the signal rail. Each car which has the motors which are used for propelling a flight has brushes respectively 60A, 60B, 62A, 62B, 64A and 64B. The brushes are located on the car so that when the car is moved in one direction along the track one set of the brushes 60A, 62A, 64A, comes in contact with the respective power rails 37, 38 and 39 and the other brush 64B comes in contact with the signal rail 40. When a flight travels around one of the end loops either for loading or unloading, it comes back into the main rail line section facing in the opposite direction. When this occurs, then brushes 60B, 62B and 64B respectively contact the-power rails 37, 38 and 39 while the brush 64A will contact the signal rail 40.

Accordingly, the brushes 60A and 60B are wired in parallel, brushes 62A and 62B are wired in parallel as are brushes 64A and 64B. The power from the brushes is connected to a motor control circuit 66, whose output is used to control the propelling motors.

Each car will have a pickup coil 68 extending below it where it can pick up a signal from a first control loop in a block when facing in one direction and from a second control loop in a block when facing in the opposite direction. Su'ch signal is amplified by an amplifier 70 and then applied to three filters or frequency detectors 71A, 71B and 71C. The outputs of these are rectified by rectifiers respectively 73A, 73B and 73C. The outputs of the rectifiers are applied to the motor control circuit to determine the amount of current permitted to flow to the motor, and thus determines the train speed. Also, the output from the rectifier must be present in order for the brakes not to be applied. In summary, the output from the rectifiers 73A, 73B and 73C are supplied to a brake control FIGS. 5A and 5B are a circuit diagram illustrating the an I rangements for the relays in the relay box whereby the control functions for this system are carried out. Four blocks are represented in order to completely illustrate the workings of Y the system. As shown by'the location of the brushes 64A and 648 respectively in contact with the signal rail and the power rail 37, the flight is in block No. 3. The direction of travel is from right to left.

In FIG. 3 there is shown a box 50 which connects through fuse boxes 52 and 41 to the rails 37, 38, 39 and 40. What is contained in the power junction box 50 as may be seen in FIG. 5A, is a transformer having its primary windings connected through suitable fuses between the signal rail and the rail 37. The secondary of the transformer is connected through a suitable rectification and filtering network 91 to a pair of output terminals 93 and94. One of these output terminals 93, is negative and connects to one terminal of a relay winding 66. It continues on to connect to a first distribution bus 98, which feeds one terminal of a second relay'winding 70. This distribution bus connects to the one terminal of all of the relay windings 70 which are associated with each block of track being controlled. The line connecting to'the terminal 93 then continues upward to a second distribution bus 95. This second distribution bus also extends to all of the K1 relays in each block, and more specifically is connected to the swinger arm 70" ofthe Kl relay in each block.

At this time it should be noted that the'relay box for each block contains a Kl relay which is a three contact double-pole double-throw relay, and a K2 relaywhich is also a triple-pole double-throw relay. The K] relay in each block has its winding designated by the reference numeral 70, its swinger arms designated by the reference numeral70, 70 and 70" and its contacts designated with the reference numerals 70A through 70F. The K2 relays similarly have their relay windings designated by the reference numeral 66, their swinger arms designated by reference numerals respectively 66', 66" and' 66" and their contacts designated by the reference numerals from 66A through 66F. I

Referring'back to the output of the rectifier circuit 41 in block 3, the terminal 94, which is a positive terminal in each block extends up to the other terminal of the winding 70'of each K1 relay in a block'and connects to the swinger arm 70 of the K1 relay in a preceding block.

Referring back to the primary winding at the transformer 90, it was previously indicated that it was connected across the signal rail and the power rail 37. In order to supply power to the secondary winding, a connection is made through a resistor 74 to the second power rail 38.

It should be borne in mind that a signal rail for a block is iso-' lated from the signal rail of the other blocks. This is done very simply by leaving an airgap between the ends of the signal rail on the order of an inch or two, which is sufficient. Ac-' cordingly, when a vehicle is within a block, the connection between the brushes 64A and 64B which respectively contact the signal rail and the first power rail serve to short out the primary winding of the transformer 60. This serves to remove-the power input to the transformer 60 whereby the K1 relay for that particular block, which is block 3, is deactivated. The Kl relay for the succeeding block, which isblock 4, where no short is present, is energized. The K1 relayfor the preceding blocks which are blocks 1 and 2, remain energized. Ac cordingly, the only K1 relay which is deenergized is the one associated with a block within which a flight is present. All other Kl relays remain energized. A K2 relay-which has one-terminal of its relay coil 66 connected to the terminal 93 of thepower supply for its own block, has its other windingterminah connected up to the contacts 70A of a K1 relay in the succeeding block. The swinger 70' which makes contact with the terminal 70A when the K1 relay is energized, is connected to the positive output terminals 64 of the next succeeding block. Accordingly, a K2 relay, in order to be energized, requires that the K1 relay in the succeeding block be energized and that the power supply in the next succeeding block, to which the K1 relay contact is connected also be energized. In the arrangement shown in HQ. 5A since the K1 relay in block 3 is deenergized, the K2 relays in blocks 2 and l are also deenergized. However, the K2 relay in the other blocks 3 and 4 are energized. As will be shown, a Kl relay controls the cnergization of one control loop in a succeedingblock and :1 K2 relay controls the energization of the other control loop in its own block.

The description that follows illustrates how the audio frequency signalling current gets turned offin the two preceding blocks when the flight is loaded. Assume that the flight is traveling from left to right. Since it is now in block 3, the K1 relay in block 3 is deenergized but the K2 relay in this block is energized and the K2 relays in the two preceding blocks are deenergized. The audio frequency signalling current (which was established as 3,000 Hertz in an embodiment of the invention which was built) is distributed over the entire system by a twist pair of wires 80, using suitably located amplifiers. To obtain speed control, 3,l Hz and 3,200 Hz were also used.

The twisted pair of wires is fedffrom a common source of signals. Periodically, amplifiers are inserted in the twisted pair in order to insure a proper signal level. One such amplifier 82, is shown on the left side of the drawing. One line from the twisted pair extends from the amplifier to terminal number one of the terminal board 84 which is positioned at each block. From terminal number 1 at the block number 4, the twisted pair lead is connected to the swinger 70". If the K1 relay is energized, as it is in block number 4, then the swinger arm is closed to the contact 70E of the relay, which is in turn connected down to terminal-3 of the terminal board 84. This energizes the loop 42 which extends in the direction of the succeeding block in the direction of travel of the flight. This would be block number 5. The return from this loop is connected to terminal 4 of the terminal board 84.

Terminal 4 connects to a contact 70F of the K1 relay and to the swinger 66" of the K2 relay. The K2 ',re1ay is in its energized state in block 4 and therefore the swinger 66" is connected to contact 66E. From contact 66E connection is made to terminal 5 of the terminal board 84. Terminal 5 connects to the loop 44 which extends back to block 3. The loop, then connects to terminal 6 on the terminal board 84. Terminal 6 is bridged back to terminal 2 of the terminal board. Terminal 2 connects back to the wire of the twister pair 80.

This wire then extends to the terminal 1 of the terminal board 84 in block 3. Tracing the other wire of the twisted pair, this extends from the amplifier down to the other end of the track where it is connected to terminal 2 of terminal board 84 in block 1. Terminal 2 is connected to terminal 6.

The K2 relay in block 1 is deenergized as may be seen by tracing the terminal of the relay coil 66in block 1 through the terminal 70A of K1 relay in block 2, the swinger arm 70', to the power supply of block 3. However, since this power supply is shorted out by the presence of the flight in that block, relay K2 in block 1 is deenergized. Relay K2 in block 2 is also deenergized essentially for the same reason. lts relay winding is connected to terminal 70 of relay K1 in block 3. Since the relay is deenergized because the power supply has been shorted, there is no further connection made to energize the winding 66 of relay K2 in block 2.

Returning now to the twisted pair 80, ithas been shown that by reason of the K2 relay in block 1 being deenergized, the

twisted pair lead is connected from terminal 2 of the terminal board 84, to terminal 6, then through the contact 66" to terminal 4 of the terminal board 84. The control loop which exat this time is energized, and thereafter through the swinger 70 to terminal 1 of the terminal board 84 in block I. Terminal 1 of the terminal boardin block one extends to terminal two of the-terminal board in block2. The connections from the terminal board to the K1 and K2 relays in the respective blocks and to the respective loops is the ,same as has been described for block 1, except that terminals 5 and 6 connect to the control loop 44 which is .acontrol looptex-tending from block 1 to block 2.

The path of the other lead ollthc twisted pair accordingly can be traced through the swinger 66" down to terminal 4 of the terminal board 84 in block lad trough control loop 42 to terminal 3 of the terminal board. Terminal3'ol the terminal board is connected to contact 70E of 'the'Kl relay in block 2, then through the swinger, 70' (relay Kl being energized) down to terminal one of the terminal board. From the description given previously of the path of the firstlead of the twisted pair, it will be recalled that this lead is connected to terminal] of the terminal board of block 2 by virtue of the states of-the K1 and K2 relays with the situation assumed, namely that the flight is present in the block 3.

From the foregoing description, it may be summarized that the presence of a flight in a particular block shorts out the DC power supply in that particular block.-The affect of this is to deenergize the K1 relay in that particular block, which other-v wise is energized, and further to deenergize the K2 relays in. the two preceding blocks. The results of these deenergizations is to prevent audio signals from being applied to the two control loops 44 in the two preceding blocks and the control loop 42 in a succeeding block. The precedingblocks represent the direction from which a loaded flight'wo'uld come and the succeeding block is in the direction'frorn 'which an empty flight wouldcome. Terminal 5 to which control loops 44 in blocks 1 and 2 are connected, goes to an open contact on relay K2. Thus, these. loops are deenergized. However,th control loops which are required for energizing a flight traveling in the opposite direction, when the flight is empty, are alive except for the single control loop 42 in block 4. This may be readily checked byobserving that the control loop 42 connects to terminals 3 and 4 of the terminal boards 84 in the respective blocks. The ter minal 3 connects to contact 70D on relay K1 in the particular block. When the relay K1 is energized the associated control loop 42 is energized. When the relay is deenergized, the as.- sociated control loop is not.

For the purpose of controlling the speed of the flights, instead of a signalling frequency of 3,000 Hertz being used, another frequency such as 3,100 Hertz or 3,200 Kilohertz may be used. When suitable detection equipment on thefflight detects the presence of this different frequency, the motor speed can be lowered accordingly. The required signals can be applied to the twisted pair at the beginning of the block. The twisted pair with the 3 Kilohertz frequency is terminated and the twisted pair for the slowdown frequency is initiated at the location where it is desired to start the slow speed operation. The slow speed operation can be extended for as many blocks as desired. Since when the flight runs at a slower speedthe distance required to stop is smaller, the length of the block is made correspondingly smaller.. Such speed changes are from the loading loop, the discharge loop, and the bypass loop for thepurpose of preventing flights from entering on to the main track until all flights comingfrom the direction which would cause a collision, have been cleared. The K2relays assist in that function. Since when any flight is present on a stretch of track, the two K2 relays in thetwo adjacent zones are deenergized, while the K2 relays in all the other blocks are energized, all that is necessary to detect whether or..not all flights have cleared from a desired stretch of track is to assign that a contact pair 'on the K2 relays to this detection function and then connect up these contact pairs in series. Accordingly, contact pair 66C and 66D have this function and swinger arm 66' is in contact with 66C when the relay is energized and in contact with 66D when it is deenergized. I

As shown in FIG. 58, a source of potential for operating the sliding switch 90 is connected to the contact 66C of the K2 relay which is in the first block of thestretch of track desired to be monitored. The swinger arm 66" of the K2 relay in this block is connected to the contact 66C of the K2 relay in the next block. The swinger arm of this next block K2 relay is connected to the contact 66C of the K2 relay in the following block. This pattern of connection is made until at the last block desired to be monitored, the swinger 66" is connected to the sliding switch operating solenoid. From the foregoing it will be seen that by the serial connection of the specified contacts and swinger arms of the K2'relays,"the sliding switch is not energized to permit a flight to advance into a sectionof track until all of the K2 relays associated with that section of track are energized, which can only'occur when flights are no longer present in that track section. I q I From the foregoing description, itwill be seen how, by employing a control system in accordance with this invention, flights can be automatically controlled in a manner to prevent collisions, in a manner to stop until a track section is clear, and in a manner to slow down where for purposes such as loading and unloading, or the like, a slow speed operation is desired. All of this is done automatically by what may be termed a distributedcont'rol system, that is, one wherein the logical functions leading to decisions which must be made are made at trackside locations instead of at a central location. The advantages of this should be obvious. One need not collect wayside signals and string wires back to the central location where a central processor processes these signals and feeds them back into wires to the location at which action must be taken. I v

Another beneficial feature of the control system in accordance with this invention, occurs whena startup is necessary after a number of flights have been collected because of a closedown of the system. Like in any other electrified railway system, should'all of the trains attempt to start up simultaneously upon the application of power to the power rails, the power demand is far greater v than that which is normally required. Calculations show that the startup power demand in a situation such as this would require power generation and carrying equipment many many times more expensive than is actually required. Of course, this does not make economic sense. Therefore, it is desirable if at all possible to start up the flights one by one. With the system described herein, this occurs automatically. When the lead flight comes to a stop within a block, the flight behind it closes the distance between the two flights until it enters the dead zone which may be two blocks behind the lead flight or one block behind the lead flight depending upon whether the flights are empty or filled. Accordingly, the flight following the lead flight coasts to a stop within the dead zone. 7

The same procedure occurs with the flights which follow. This afl'ectively is the situation which occurs when the flights are gathered in either the emptying or loading loop or in the bypass loop. Then, when the lead flightstarts up, none of the following flights can start up until the lead flight has traveled at least one block whereby the control loop for the flight behind it is energized enabling it to start up. Again, this same pattern is followed with the succeeding flights resulting in a one-by-one startup. As a consequence, there is no overloading problem nor is there an overcapacity requirement on the part of the power systemfor the railway.

While the embodiment of this invention is described as using relays K1 and K2, those skilled in the art will appreciate that other equipment, such as solid-state devices may be used in place of the relays to perform the same functions, without departing from the spirit and scope of this invention. Therefore the apparatus described for carrying out the invention should be considered as exemplary and not as limiting.

a plurality of wire control loops ea h of which extends for a predetermined distance adjacent the rails of said railroad to define a sequence of loop distances'called blocks;

each of the wire control loops adjacent the rails in a block including a first control loop which is adjacent one side of the rails, and a second control loop which is adjacent the other side of the rails; j I

means for generating electrical signals at a predetermined frequency; f 7

means for applying said electrical signals to the first and second wire control loops in each block;

means on a train for detecting. the-presence of electrical signals in a first wire control loopwhen said train is facing in one direction and in a second 'wire controlloop when said train is facing in the oppositedirection;

means on the train responsive to detected electrical signals from a first or a second of said wire control loops for I enabling said train to be propelled and to the absence'of said detectedelectrical signals to bring said train to a stop; and

means responsive to the presence of a train within a block for interrupting the application of electrical signals to the wire control loops in the preceding. block, including means for interrupting the application of electrical signals in the first wire control loop in a preceding block when said train is proceeding in one direction and in a second wire control loop in a preceding block when said train is proceeding in the opposite direction.

2. A control system as recited in claim .1 wherein said means on said train for detecting the presenceof electrical signals in-' cludes means for detecting the frequency of said-electrical signals; said means on said train responsive to said detected 1 signals includes means responsive'to the frequency detected to control the speed of said train accordingly.

3. A control system for controlling trains of a railroad as recited in claim 1 wherein there is-provided for each block a normally operative relay means and means including the normally operative relay means for each block for applying electrical signals from said means for generating electrical signals to the wire control loop for a block preceding the one of said normally operative relay means, said normally operative relay means at each block includes power supply means forapplying power to a relay means to maintain it normally operative; said means responsive to the presence of a train within a block for rendering the normally operative relay means for said block inoperative includes means carried by said train for disenabling said power supply means whilesaid train is within said block.

4. A control system as recited in claim 3 wherein there is included means responsive to all of the normally operative relay means for a predetermined number of blocks being normally operative to indicate that there are no trains present in the said predetermined number of blocks. 7 5. A control system for controlling trains of a railroad comprising:

a plurality of first wire control loops each of which extends for a predetermined distance adjacent one side of the rails of said railroad to define a sequence of loop distances called blocks;

a plurality of second wire control loops each of which extends for said predetermined distance adjacent the other side of said rails of said railroad and each of which is coextensive with a first wire control loop;

a first relay means for each block;

a second relay means for each block;

a power supply means for each block;

means connecting each power supply means for each block to energize the first relay means for that block;

means including an energized first relay means of a succeeding block for connecting each power supply means for each second succeeding block to energize the second relay means for each block; i

means for generating electrical signals at a predetermined frequency; l-

means including each energized first relay means in a block for feeding said electrical signals to-each first wire control loop in said block;

means including each energized second relay means in a block for feeding said electrical signals to each second wire control loop in a block;

means on a train for detecting the presence of said electrical signals in a first wire control loop. when said train is heading in one direction and for detecting the presence of said electrical signals, in a second wire control loop when said train is heading in the opposite direction;

means on said train responsive to said detected signals for enabling said train to be propelledand to the absence of said detected signals to cause'said train to stop; and

means responsive to the presence of said train within a block to disenable the power supply for that block wherebythe first relay means for-that block is deenergized, the second relay means for the two preceding blocks are deenergized and electrical signals are removed from the second wire control loops for the two preceding blocks and the first wire control loop for the succeeding block. i i

6. A control system for controlling trains as recited in claim wherein:

said power supply means includes a separate signal rail extending the length of each block but separated from every other block; 1

a first and second power rail extending throughout all of said blocks;

a connection between each signal first power rail; and transformer means for each power supply means in a block having a first and second input terminal respectively connected to the signal rail of a block and to the second power rail. I f t 7. A control system for controlling a train as recited in claim 6 wherein said means responsive vto the presence of a train within a block to disenable the powersupply within that block includes brush means carried by a. train for producing a shorted connection between a first power Trail and a signal rail to thereby prevent-the application of' power to the transformer means within the block. Y

8. A control system as recited in claim 7 wherein there is included a means responsive to all of thesecond relay means for a predetermined number of blocks being energized to indicate that there are no trains present within said predetermined number of blocks.

9. A control system as recited in claim 5 wherein said means on said train for detecting the presence of electrical signals inra il in a block and said cludes means for detecting the frequency of said electrical signals; said means on said train responsive to said detected signals includes means responsive. to thefrequency detected tocontrol the speed of said train accordingly. 

1. A control system for controlling trains of a railroad comprising: a plurality of wire control loops each of which extends for a predetermined distance adjacent the rails of said railroad to define a sequence of loop distances called blocks; each of the wire control loops adjacent the rails in a block including a first control loop whiCh is adjacent one side of the rails, and a second control loop which is adjacent the other side of the rails; means for generating electrical signals at a predetermined frequency; means for applying said electrical signals to the first and second wire control loops in each block; means on a train for detecting the presence of electrical signals in a first wire control loop when said train is facing in one direction and in a second wire control loop when said train is facing in the opposite direction; means on the train responsive to detected electrical signals from a first or a second of said wire control loops for enabling said train to be propelled and to the absence of said detected electrical signals to bring said train to a stop; and means responsive to the presence of a train within a block for interrupting the application of electrical signals to the wire control loops in the preceding block, including means for interrupting the application of electrical signals in the first wire control loop in a preceding block when said train is proceeding in one direction and in a second wire control loop in a preceding block when said train is proceeding in the opposite direction.
 2. A control system as recited in claim 1 wherein said means on said train for detecting the presence of electrical signals includes means for detecting the frequency of said electrical signals; said means on said train responsive to said detected signals includes means responsive to the frequency detected to control the speed of said train accordingly.
 3. A control system for controlling trains of a railroad as recited in claim 1 wherein there is provided for each block a normally operative relay means and means including the normally operative relay means for each block for applying electrical signals from said means for generating electrical signals to the wire control loop for a block preceding the one of said normally operative relay means, said normally operative relay means at each block includes power supply means for applying power to a relay means to maintain it normally operative; said means responsive to the presence of a train within a block for rendering the normally operative relay means for said block inoperative includes means carried by said train for disenabling said power supply means while said train is within said block.
 4. A control system as recited in claim 3 wherein there is included means responsive to all of the normally operative relay means for a predetermined number of blocks being normally operative to indicate that there are no trains present in the said predetermined number of blocks.
 5. A control system for controlling trains of a railroad comprising: a plurality of first wire control loops each of which extends for a predetermined distance adjacent one side of the rails of said railroad to define a sequence of loop distances called blocks; a plurality of second wire control loops each of which extends for said predetermined distance adjacent the other side of said rails of said railroad and each of which is coextensive with a first wire control loop; a first relay means for each block; a second relay means for each block; a power supply means for each block; means connecting each power supply means for each block to energize the first relay means for that block; means including an energized first relay means of a succeeding block for connecting each power supply means for each second succeeding block to energize the second relay means for each block; means for generating electrical signals at a predetermined frequency; means including each energized first relay means in a block for feeding said electrical signals to each first wire control loop in said block; means including each energized second relay means in a block for feeding said electrical signals to each second wire control loop in a block; means on a train for detecting the presence of said electrical signals in a firSt wire control loop when said train is heading in one direction and for detecting the presence of said electrical signals, in a second wire control loop when said train is heading in the opposite direction; means on said train responsive to said detected signals for enabling said train to be propelled and to the absence of said detected signals to cause said train to stop; and means responsive to the presence of said train within a block to disenable the power supply for that block whereby the first relay means for that block is deenergized, the second relay means for the two preceding blocks are deenergized and electrical signals are removed from the second wire control loops for the two preceding blocks and the first wire control loop for the succeeding block.
 6. A control system for controlling trains as recited in claim 5 wherein: said power supply means includes a separate signal rail extending the length of each block but separated from every other block; a first and second power rail extending throughout all of said blocks; a connection between each signal rail in a block and said first power rail; and transformer means for each power supply means in a block having a first and second input terminal respectively connected to the signal rail of a block and to the second power rail.
 7. A control system for controlling a train as recited in claim 6 wherein said means responsive to the presence of a train within a block to disenable the power supply within that block includes brush means carried by a train for producing a shorted connection between a first power rail and a signal rail to thereby prevent the application of power to the transformer means within the block.
 8. A control system as recited in claim 7 wherein there is included a means responsive to all of the second relay means for a predetermined number of blocks being energized to indicate that there are no trains present within said predetermined number of blocks.
 9. A control system as recited in claim 5 wherein said means on said train for detecting the presence of electrical signals includes means for detecting the frequency of said electrical signals; said means on said train responsive to said detected signals includes means responsive to the frequency detected to control the speed of said train accordingly. 